Identification of 36 kDa phosphoprotein in fibrous sheath of hamster spermatozoa

Specific autoantigens identified by sera obtained from mice that are immunized with testicular germ cells alone

There are various autoimmunogenic antigens (AIs) in testicular germ cells (TGCs) recognized as foreign by the body's immune system. However, there is little information of TGC-specific AIs being available. The aim of this study is to identify TGC-specific AIs. We have previously established that immunization using viable syngeneic TGC can also induce murine experimental autoimmune orchitis (EAO) without using any adjuvant. This study is to identify TGC-specific AIs by TGC liquid chromatography-tandem mass spectrometry analysis, followed by two-dimensional gel electrophoresis that reacted with serum IgG from EAO mice. In this study, we identified 11 TGC-specific AIs that reacted with serum from EAO mice. Real-time RT-PCR analysis showed that the mRNA expressions of seven TGC-specific AIs were significantly higher in only mature testis compared to other organs. Moreover, the recombinant proteins of identified 10 (except unnamed protein) TGC-specific AIs were created by using human embryonic kidney 293 (HEK293) cells and these antigencities were reconfirmed by Western blot using EAO serum reaction. These results indicated Atp6v1a, Hsc70t, Fbp1 and Dazap1 were candidates for TGC-specific AIs. Identification of these AIs will facilitate new approaches for understanding infertility and cancer pathogenesis and may provide a basis for the development of novel therapies.

JMJD1A is a signal-sensing scaffold that regulates acute chromatin dynamics via SWI/SNF association for thermogenesis

Histone 3 lysine 9 (H3K9) demethylase JMJD1A regulates β-adrenergic-induced systemic metabolism and body weight control. Here we show that JMJD1A is phosphorylated at S265 by protein kinase A (PKA), and this is pivotal to activate the β1-adrenergic receptor gene (Adrb1) and downstream targets including Ucp1 in brown adipocytes (BATs). Phosphorylation of JMJD1A by PKA increases its interaction with the SWI/SNF nucleosome remodelling complex and DNA-bound PPARγ. This complex confers β-adrenergic-induced rapid JMJD1A recruitment to target sites and facilitates long-range chromatin interactions and target gene activation. This rapid gene induction is dependent on S265 phosphorylation but not on demethylation activity. Our results show that JMJD1A has two important roles in regulating hormone-stimulated chromatin dynamics that modulate thermogenesis in BATs. In one role, JMJD1A is recruited to target sites and functions as a cAMP-responsive scaffold that facilitates long-range chromatin interactions, and in the second role, JMJD1A demethylates H3K9 di-methylation.

Demethylase JMJD1A activates thermogenesis-related target genes in response to β-adrenergic hormones. Here, the authors show that phosphorylation of JMJD1A at S265 increases its interaction with the SWI/SNF chromatin remodeler, leading to long-range chromatin interactions and target gene activation.

A comprehensive proteomic approach to identifying capacitation related proteins in boar spermatozoa

BACKGROUND

Mammalian spermatozoa must undergo capacitation, before becoming competent for fertilization. Despite its importance, the fundamental molecular mechanisms of capacitation are poorly understood. Therefore, in this study, we applied a proteomic approach for identifying capacitation-related proteins in boar spermatozoa in order to elucidate the events more precisely. 2-DE gels were generated from spermatozoa samples in before- and after-capacitation. To validate the 2-DE results, Western blotting and immunocytochemistry were performed with 2 commercially available antibodies. Additionally, the protein-related signaling pathways among identified proteins were detected using Pathway Studio 9.0.

RESULT

We identified Ras-related protein Rab-2, Phospholipid hydroperoxide glutathione peroxidase (PHGPx) and Mitochondrial pyruvate dehydrogenase E1 component subunit beta (PDHB) that were enriched before-capacitation, and NADH dehydrogenase 1 beta subcomplex 6, Mitochondrial peroxiredoxin-5, (PRDX5), Apolipoprotein A-I (APOA1), Mitochondrial Succinyl-CoA ligase [ADP-forming] subunit beta (SUCLA2), Acrosin-binding protein, Ropporin-1A, and Spermadhesin AWN that were enriched after-capacitation (>3-fold) by 2-DE and ESI-MS/MS. SUCLA2 and PDHB are involved in the tricarboxylic acid cycle, whereas PHGPx and PRDX5 are involved in glutathione metabolism. SUCLA2, APOA1 and PDHB mediate adipocytokine signaling and insulin action. The differentially expressed proteins following capacitation are putatively related to sperm functions, such as ROS and energy metabolism, motility, hyperactivation, the acrosome reaction, and sperm-egg interaction.

CONCLUSION

The results from this study elucidate the proteins involved in capacitation, which may aid in the design of biomarkers that can be used to predict boar sperm quality.

Regulation and disruption of hamster sperm hyperactivation by progesterone, 17β-estradiol and diethylstilbestrol

Purpose

Hyperactivation of hamster sperm is dose-dependently enhanced by progesterone (P) and 17β-estradiol (E). In the first part of the present study, enhancement of hyperactivation in response to the concentrations of P and E was examined in detail and in the second part, it was examined whether enhancement of hyperactivation by P and E was disrupted by diethylstilbestrol (DES).

Methods

Hamster spermatozoa were hyperactivated by incubation in modified Tyrode's albumin lactate pyruvate medium with P, E and/or DES. After spermatozoa were recorded using a video-microscope, observations were quantified by manually counting the numbers of total, motile and hyperactivated spermatozoa.

Results

Hyperactivation was enhanced in response to the concentrations of P and E. When spermatozoa were exposed to DES with E, moreover, DES significantly and strongly suppressed P-enhanced hyperactivation by accelerating the effect of E, but DES itself only weakly suppressed P-enhanced hyperactivation.

Conclusions

Enhancement of hyperactivation was regulated by the concentrations of P and E, suggesting that in vivo hamster spermatozoa are hyperactivated through "monitoring" these concentrations in the oviduct. DES in combination with E suppressed P-enhanced hyperactivation, suggesting that DES significantly disrupts hyperactivation by acting as an accelerator of the effect of E.

Sperm phosphoproteomics: historical perspectives and current methodologies

Mammalian sperm are differentiated germ cells that transfer genetic material from the male to the female. Owing to this essential role in the reproductive process, an understanding of the complex mechanisms that underlie sperm function has implications ranging from the development of novel contraceptives to the treatment of male infertility. While the importance of phosphorylation in sperm differentiation, maturation and fertilization has been well established, the ability to directly determine the sites of phosphorylation within sperm proteins and to quantitate the extent of phosphorylation at these sites is a recent development that has relied almost exclusively on advances in the field of proteomics. This review will summarize the work that has been carried out to date on sperm phosphoproteomics and discuss how the resulting qualitative and quantitative information has been used to provide insight into the manner in which protein phosphorylation events modulate sperm function. The authors also present the proteomics process as it is most often utilized for the elucidation of protein expression, with a particular emphasis on the way in which the process has been modified for the analysis of protein phosphorylation in sperm.

Progesterone-enhanced sperm hyperactivation through IP3-PKC and PKA signals

Propose

The present study examined whether regulation of progesterone-enhanced hyperactivation of spermatozoa is associated with the production of inositol 1,4,5-trisphosphate (IP₃) and diacylglycerol (DAG) by phospholipase C (PLC) and cyclic adenosine monophosphate (cAMP) by adenylate cyclase (AC), as well as activation of protein kinase C (PKC) and protein kinase A (PKA).

Methods

Hamster spermatozoa were hyperactivated by incubation for 4 h in modified Tyrode's albumin lactate pyruvate (mTALP) medium. In order to examine the effects of IP₃ receptor (IP₃R), PKC and PKA on progesterone-enhanced hyperactivation, their inhibitors (xestospongin C, bisindolylmaleimide 1 and H-89) were used.

Results

Progesterone-enhanced hyperactivation was significantly suppressed by the inhibitors of IP₃R, PKC and PKA.

Conclusions

The results suggest that progesterone-enhanced sperm hyperactivation occurs through two signal pathways. One is an intracellular Ca²⁺ signal through production of IP₃ and DAG by PLC, binding of IP₃ to IP₃R and activation of PKC by DAG and Ca²⁺. The other is a cAMP-PKA signal through production of cAMP by AC and activation of PKA by cAMP.

Identification and validation of mouse sperm proteins correlated with epididymal maturation

Sperm need to mature in the epididymis to become capable of fertilization. To understand the molecular mechanisms of mouse sperm maturation, we conducted a proteomic analysis using saturation dye labeling to identify proteins of caput and cauda epididymal sperm that exhibited differences in amounts or positions on two-dimensional gels. Of eight caput epididymal sperm-differential proteins, three were molecular chaperones and three were structural proteins. Of nine cauda epididymal sperm-differential proteins, six were enzymes of energy metabolism. To validate these proteins as markers of epididymal maturation, immunoblotting and immunofluorescence analyses were performed. During epididymal transit, heat shock protein 2 was eliminated with the cytoplasmic droplet and smooth muscle γ-actin exhibited reduced fluorescence from the anterior acrosome while the signal intensity of aldolase A increased, especially in the principal piece. Besides these changes, we observed protein spots, such as glutathione S-transferase mu 5 and the E2 component of pyruvate dehydrogenase complex, shifting to more basic isoelectric points, suggesting post-translational changes such dephosphorylation occur during epididymal maturation. We conclude that most caput epididymal sperm-differential proteins contribute to the functional modification of sperm structures and that many cauda epididymal sperm-differential proteins are involved in ATP production that promotes sperm functions such as motility.

Serotonin-enhanced hyperactivation of hamster sperm

The effects of serotonin on reproductive function were examined using hamster spermatozoa. When serotonin at concentrations from 1 fmol/l to 1 μmol/l was added to modified Tyrode's albumin lactate pyruvate (mTALP) medium, hyperactivation was significantly enhanced. Agonists and antagonists of 5-hydroxytryptamine hydrochloride (5-HT) receptors (5-HT(2) and 5-HT(4) receptors) were added to the medium. Both 5-HT(2) and 5-HT(4) receptor agonists significantly enhanced hyperactivation, although the effect was greater than the former. However, both 5-HT(2) and 5-HT(4) receptor antagonists significantly suppressed serotonin-enhanced hyperactivation, with the former suppressing stimulation by a lower concentration of serotonin than the latter. These results indicate that serotonin enhances hyperactivation via 5-HT(2) and/or 5-HT(4) receptors in a dose-dependent manner.

Non-genomic regulation of mammalian sperm hyperactivation

Although it has been suggested that the acrosome reaction is induced through non-genomic regulation in a ligand-dependent manner, it is not known whether hyperactivation is similarly regulated. Progesterone and melatonin have been identified as ligands that regulate hyperactivation, the former through non-genomic regulation with phospholipase C and the latter most likely through a reactive oxygen species-mitogen activated protein kinase cascade. Both may be involved in spontaneous regulation of hyperactivation via tyrosine phosphorylation. The concentration of many hormones changes according to environmental conditions and biological rhythms, which will modulate ligand-dependent regulation of hyperactivation.

Hamster sperm capacitation: role of pyruvate dehydrogenase A and dihydrolipoamide dehydrogenase

Recently, we demonstrated that pyruvate dehydrogenase A2 (PDHA2) is tyrosine phosphorylated in capacitated hamster spermatozoa. In this report, using bromopyruvate (BP), an inhibitor of PDHA, we demonstrated that hamster sperm hyperactivation was blocked regardless of whether PDHA was inhibited prior to or after the onset of hyperactivation, but the acrosome reaction was blocked only if PDHA was inhibited prior to the onset of the acrosome reaction. Further, inhibition of PDHA activity did not inhibit capacitation-associated protein tyrosine phosphorylation observed in hamster spermatozoa. It is demonstrated that the essentiality of PDHA for sperm capacitation is probably dependent on its ability to generate effectors of capacitation such as reactive oxygen species (ROS) and cAMP, which are significantly decreased in the presence of BP. MICA (5-methoxyindole-2-carboxylic acid, a specific inhibitor of dihydrolipoamide dehydrogenase [DLD]), another component of the pyruvate dehydrogenase complex (PDHc), also significantly inhibited ROS generation and cAMP levels thus implying that these enzymes of the PDHc are required for ROS and cAMP generation. Furthermore, dibutryl cyclic adenosine monophosphate could significantly reverse the inhibition of hyperactivation observed in the presence of BP and inhibition of acrosome reaction observed in the presence of BP or MICA. The calcium ionophore, A23187, could also significantly reverse the inhibitory effect of BP and MICA on sperm acrosome reaction. These results establish that PDHA is required for hamster sperm hyperactivation and acrosome reaction, and DLD is required for hamster acrosome reaction. This study also provides evidence that ROS, cAMP, and calcium are involved downstream to PDHA.

Activity of Pyruvate Dehydrogenase A (PDHA) in Hamster Spermatozoa Correlates Positively with Hyperactivation and Is Associated with Sperm Capacitation1

Unravelling the molecular basis of capacitation is crucial to our understanding the basis of acquisition of fertilization competence by spermatozoa. In two recent studies, we have demonstrated that dihydrolipoamide dehydrogenase, which is a post-pyruvate metabolic enzyme and one of the components of pyruvate dehydrogenase complex, undergoes capacitation-dependent tyrosine phosphorylation, and that the activity of the enzyme correlates with capacitation events in the hamster spermatozoa. However, it is not clear as to whether other components of the pyruvate dehydrogenase complex are also crucial for sperm capacitation. In this report, we have identified pyruvate dehydrogenase A2 (PDHA2), a constituent of pyruvate dehydrogenase A (PDHA), which is a component of pyruvate dehydrogenase complex that exhibits tyrosine phosphorylation during hamster spermatozoal capacitation. This is the first report showing that hamster sperm PDHA2 is a testis-specific phosphotyrosine that is associated with the fibrous sheath of hamster spermatozoa. The localization of PDHA2 in spermatozoa was investigated using antibodies to PDHA, which is the active tetrameric protein that consists of a homodimer of PDHA2 and PDHB. Both immunofluorescence and confocal studies indicated a unique non-canonical, extramitochondrial localization for PDHA in the principal piece of hamster spermatozoa. It was also observed that PDHA colocalized with AKAP4 in the fibrous sheath of the spermatozoon. The enzymatic activity of PDHA was positively correlated with hyperactivation but not with the acrosome reaction. Given the localization of PDHA and the evidence that its activity correlates positively with hyperactivation and that its PDHA2 subunit exhibits capacitation-associated protein tyrosine phosphorylation, it appears that PDHA2 is associated with the process of capacitation.

New fibrous sheath anomaly in spermatozoa of men with consanguinity

OBJECTIVE

The cause of the sperm motility impairment was investigated in infertile men.

DESIGN

Case report.

SETTING

University-based andrology laboratory.

PATIENTS

Two unrelated consanguineous patients.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The sperm flagella lengths were measured using quantitative analysis software and their ultrastructural anomalies were quantitatively recorded.

RESULT(S)

A total of 67.5% of the flagella were truncated, and 100% lacked the medium region of the ribs of the fibrous sheath.

CONCLUSION(S)

The data suggested a morphogenetic anomaly at the stage where rib precursors are formed during spermiogenesis. The consanguinity of these patients suggested a genetic origin for this newly discovered anomaly of the human sperm's fibrous sheath. The family tree appears to indicate an autosomal recessive inheritance.

Profiling of proteins phosphorylated or dephosphorylated during hyperactivation via activation on hamster spermatozoa

Background and Aims:  It has been widely accepted that sperm hyperactivation is regulated by protein phosphorylations. But, the sperm hyperactivation phosphorylation pathway is not well understood yet because several different proteins have been detected in other studies. In order to understand the phosphorylation pathway that regulates hyperactivation, we established how to extract sperm protein completely and detected proteins that were phosphorylated during hyperactivation. Methods:  Protein phosphorylation of hamster spermatozoa was detected by western blotting using antiphospho-amino acid monoclonal antibodies or the SELDI ProteinChip system with IMAC-Ga(III). Results:  We detected 75 protein/peptide phosphoryations using the method established in the present study. Tyrosine phosphorylations occurred during hyperactivation. Serine or threonine phosphorylations occurred for 30 min. Furthermore, four of the serine or threonine phosphorations were phosphorylated by A-kinase. As for peptides, 15 peptides were dephosphorylated for 30 min. Other peptides were phosphorylated during hyperactivation. Conclusions:  Because most of the proteins detected in the present study have been described previously, we could detect comprehensive protein phosphorylations. Moreover, we also detected many novel phosphopeptides. Although we did not understand the role of peptide, it was likely that motility was basically regulated by serine/threonine phosphorylations and hyperactivation was mainly regulated by tyrosine phosphorylations. (Reprod Med Biol 2006; 5: 123-135).

Profiling of proteins phosphorylated or dephosphorylated during hyperactivation via activation on hamster spermatozoa

Background and Aims:  It has been widely accepted that sperm hyperactivation is regulated by protein phosphorylations. But, the sperm hyperactivation phosphorylation pathway is not well understood yet because several different proteins have been detected in other studies. In order to understand the phosphorylation pathway that regulates hyperactivation, we established how to extract sperm protein completely and detected proteins that were phosphorylated during hyperactivation. Methods:  Protein phosphorylation of hamster spermatozoa was detected by western blotting using antiphospho-amino acid monoclonal antibodies or the SELDI ProteinChip system with IMAC-Ga(III). Results:  We detected 75 protein/peptide phosphoryations using the method established in the present study. Tyrosine phosphorylations occurred during hyperactivation. Serine or threonine phosphorylations occurred for 30 min. Furthermore, four of the serine or threonine phosphorations were phosphorylated by A-kinase. As for peptides, 15 peptides were dephosphorylated for 30 min. Other peptides were phosphorylated during hyperactivation. Conclusions:  Because most of the proteins detected in the present study have been described previously, we could detect comprehensive protein phosphorylations. Moreover, we also detected many novel phosphopeptides. Although we did not understand the role of peptide, it was likely that motility was basically regulated by serine/threonine phosphorylations and hyperactivation was mainly regulated by tyrosine phosphorylations. (Reprod Med Biol 2006; 5: 123-135).

Multiple glycolytic enzymes are tightly bound to the fibrous sheath of mouse spermatozoa

The fibrous sheath is a cytoskeletal structure located in the principal piece of mammalian sperm flagella. Previous studies showed that glyceraldehyde 3-phosphate dehydrogenase, spermatogenic (GAPDHS), a germ cell-specific glycolytic isozyme that is required for sperm motility, is tightly bound to the fibrous sheath. To determine if other glycolytic enzymes are also bound to this cytoskeletal structure, we isolated highly purified fibrous sheath preparations from mouse epididymal sperm using a sequential extraction procedure. The isolated fibrous sheaths retain typical ultrastructural features and exhibit little contamination by axonemal or outer dense fiber proteins in Western blot analyses. Proteomic analysis using peptide-mass fingerprinting and MS/MS peptide fragment ion matching identified GAPDHS and two additional glycolytic enzyme subunits, the A isoform of aldolase 1 (ALDOA) and lactate dehydrogenase A (LDHA), in isolated fibrous sheaths. The presence of glycolytic enzymes in the fibrous sheath was also examined by Western blotting. In addition to GAPDHS, ALDOA, and LDHA, this method determined that pyruvate kinase is also tightly bound to the fibrous sheath. These data support a role for the fibrous sheath as a scaffold for anchoring multiple glycolytic enzymes along the length of the flagellum to provide a localized source of ATP that is essential for sperm motility.

Role of tyrosine phosphorylation in sperm capacitation / acrosome reaction

Capacitation is an important physiological pre-requisite before the sperm cell can acrosome react and fertilize the oocyte. Recent reports from several laboratories have amply documented that the protein phosphorylation especially at tyrosine residues is one of the most important events that occur during capacitation. In this article, we have reviewed the data from our and other laboratories, and have constructed a heuristic model for the mechanisms and molecules involved in capacitation/acrosome reaction.

Identification of 66 kDa phosphoprotein associated with motility initiation of hamster spermatozoa

Background and Aims:  Sperm motility is regulated by protein phosphorylation. The 66 kDa protein obtained from hamster sperm flagella was phosphorylated at serine residues associated with the motility initiation. In order to understand the regulatory mechanism of sperm motility, the 66 kDa protein was identified in the present study. Methods:  The 66 kDa protein was purified by 2-D gel electrophoresis and identified by matrix-assisted laser desorption ionization mass spectrometry, liquid chromatography-tandem mass spectrometry and peptide sequencer. Results:  The 66 kDa protein was tubulin β chain. Conclusion:  The 66 kDa protein is one of the tubulin β chain isoforms and phosphorylated in relation to the motility initiation. (Reprod Med Biol 2004; 3: 133-139).